Organic light emitting diodes (“OLEDs”) are known to have many desirable qualities for use in displays. For example, they can produce bright displays, they can be manufactured on flexible substrates, they have low power requirements, and they do not require a backlight. OLEDs can be manufactured to emit different colours of light. This makes possible their use in full colour displays. Furthermore, their small size allows for their use in high resolution displays.
The use of OLEDs in displays is currently limited by, among other things, their longevity. As the OLED display is used, the luminance of the display decreases. In order to produce a display that can produce the same quality of display output repeatedly over a period of time (for example, greater then 1000 hours) it is necessary to compensate for this degradation in luminance.
One method of determining the luminance degradation is by measuring it directly. This method measures the luminance of a pixel for a given driving current. This technique requires a portion of each pixel to be covered by the light detector. This results in a lower aperture and resolution.
Another technique is to predict the luminance degradation based on the accumulated drive current applied to the pixel. This technique suffers in that if the information pertaining to the accumulated drive current is lost or corrupted (such as by power failure) the luminance correction cannot be performed.
There is therefore a need for a method and associated system for determining the luminance degradation of an OLED that does not result in a decrease in the aperture ratio, yield or resolution and that does not rely on information about the past operation of the OLED to compensate for the degradation.